Miami-Dade County’s unusual request for ideas to develop 120 acres of vacant land around its biggest attraction has drawn two very different proposals.

The operators of a German dinosaur park that’s populated by life-sized, accurate replicas of prehistoric animals want to build the same at the zoo. It’s no Jurassic Park, though. The Dinosaur Open Air Museum Miami would tell the story of the rise and fall of the dinosaur along a two-mile trail detailing “the evolution of vertebrate life through geological time” — a prequel of sorts to Zoo Miami’s living animals.

And 20th Century Fox, the Hollywood movie and TV giant, wants to build Miami Wilds, its own near-$1 billion version of Universal Studios, complete with Ice Age-themed rides (yes, there would be snow) a resort hotel, a water park, a retail and entertainment district, a daily samba parade inspired by Rio, exploding volcanoes, and rides through the sinking Titanic and the entrails of the Nostromo, the seriously disturbing spaceship from Alien.

The $15 million dino park would be far more modestly scaled, and focused on “actual science’’ and education, the company’s proposal says. It would even have a staff paleontologist. And, no, the dinos won’t be chasing anyone down a Jurassic river (that one’s in Orlando). Its 250 dinosaurs would be made of weather-resistant, fiberglass-reinforced resin, and decidedly non-moving.

The German company, Dinosaurier-Park International, will make a formal public presentation to the county on Monday, following a presentation by Fox last month.

Right now, no one involved is talking. The proposals, submitted in response to a public invitation by the county nine months ago, are under a so-called cone of silence, designed to bar lobbying during consideration.

But Fox executives told county officials last month that their proposed attraction would bring “substantial’’ economic benefits to the county, draw millions of visitors from around the world, boost attendance at the zoo and its little-known companion, the Gold Coast Railroad Museum, and provide a family-friendly commercial and entertainment center for South Miami-Dade on a par with South Beach.

This marks the county’s second attempt at redeveloping its zoo properties. An earlier attempt, in 2009, foundered after drawing two responses officials deemed unfeasible.

An evaluation team will make recommendations to Miami-Dade Mayor Carlos Gimenez, maybe by the end of the year, said Miami-Dade Commissioner Dennis Moss, whose district includes a large stretch of South Miami-Dade and who has long pushed for a resort-type park at the zoo property. Moss said he could not comment further, citing the cone of silence.

Under the terms of the invitation, the county could pick either proposal or do nothing. It could also select both, since there may be ample space to accommodate the two attractions. The land being made available includes the zoo’s vast parking lots and land along the main drive into the attraction, including parcels on Southwest 152nd Street.

There are some big caveats.

Though the dinosaur group would finance its park in full, Fox, which would privately finance $800 million of the cost of Miami Wilds, is looking for $130 million from the cash-strapped county. One reason for the public money: Development of the Miami Wilds attraction would also require moving a U.S. Coast Guard communications facility now on the site, which Fox officials warn in their proposal could take years.

But both proponents say there would be a big payoff for the county and South Miami-Dade, which has long lagged economically.

Fox projects its attraction, propelled by the company’s marketing clout and the global popularity of its films, would draw three million visitors a year, half from out of town. The company would pay the county more than $37 million during the first 10 years of a 99-year-lease. It would also provide jobs, restaurants, movie theaters and retail shops for South Miami-Dade residents, the plan says.

The Dinosaur Museum would pay the county $150,000 a year to lease 20 to 25 acres, generate annual revenues of as much as $13 million, and lure at least 400,000 people a year, the proposal says.

The original dino park, which opened 20 years ago, is in Münchehagen in northern Germany and draws 150,000 people a year, the company, which operates other parks and museum exhibits around the world, says. The sister company that produces the dinosaurs, Wolter Design, also provides them to museums and parks across the globe.

The proposed Miami Wilds attraction would comprise a 70-acre Adventure Park on the north end of the property, a 16-acre Adventure Beach Water Park nearer the existing zoo, and a retail village along 152nd Street, all connected by a nature trail. The retail village would include movie theaters where Fox could hold local red-carpet premieres and would be accessible to visitors without entering the theme park gate, executives said.

Next to the village would be a sports meadow that could be used for soccer tournaments, music festivals and other gatherings.

A 400-room hotel would be located by the zoo entrance, and could provide views from its rooms into the zoo, said project architect and planner Bernard Zyscovich.

Fox also proposes building a Sony Music theater where the music label could have its stars perform in an “intimate’’ setting.

The company executives say Fox is getting into building theme parks in a big way. Its first will open soon in Malaysia at Resorts World Genting, owned by the consortium that is trying to build a casino resort in downtown Miami. The Miami theme park would be the company’s flagship, they said.

If approved, Miami Wilds could be built in phases and completed by 2020.